Coenzyme Q10 is a type of coenzyme Q (molecular formula: C59H90O4, molecular weight: 863.36) found in higher animals, and it is also known as ubidecarenone. Coenzyme Q10 is not only bioactive as a coenzyme, but is also known as a vitamin-like substance having an effect of improving oxygen utilization efficiency. In addition to acting on congestive tissue, Coenzyme Q10 is believed to also stabilize biological membranes and exhibit antioxidant and other effects, while it has been clinically shown to have pharmacological effects that ameliorate symptoms of angina, cardiac failure, ischemic heart disease and muscular dystrophy. It has, in addition, been reported to be effective for prevention and treatment of hypertension, arteriosclerosis, heart disease, diabetes and periodontal disease, as well as for prevention of carcinostatic or psychotropic agent side-effects, and for fatigue refreshment and motor function recovery. Coenzyme Q10 is highly bioactive and highly safe for the human body.
In recent years, coenzyme Q10 has been approved for use as a food, and is becoming important as a material for health foods.
However, coenzyme Q10 is a lipophilic solid with a low melting point and hardly soluble in water. The bioavailability of orally ingested coenzyme Q10 is therefore very low. Also, coenzyme Q10 is unstable and decomposes under light to produce hydroquinones, ubichromenol and the like.
As a composition providing increased bioavailability of coenzyme Q10 there has been proposed a coenzyme Q10-containing composition obtained by preparing coenzyme Q10 as an aqueous emulsion using a polyglycerin fatty acid ester as the emulsifier, mixing the emulsion with an aqueous solution containing a water-soluble macromolecular substance at a weight of 3-fold with respect to ubiquinone, and spray drying the mixture (JP59-51214A). There has also been proposed production of fat-soluble substance aqueous liquid formulations, by emulsification of a fat-soluble substance such as coenzyme Q10 with an emulsifier such as a glycerin fatty acid ester, sucrose fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene hydrogenated castor oil or the like, a polyhydric alcohol and water (JP2000-212066A). In addition, there has been proposed production of a coenzyme Q10-containing emulsified composition obtained from coenzyme Q10 using an oil-phase component such as a vegetable oil or fatty acid ester, a polyhydric alcohol, and an emulsifier such as a glycerin fatty acid ester (JP2003-238396A). However, because emulsifiers such as glycerin fatty acid esters and sucrose fatty acid esters are highly viscous liquid substances, it is necessary to add large amounts of excipients to obtain solid compositions from the emulsions obtained using such emulsifiers, and this not only limits the coenzyme Q10 content but also lowers manageability as a result of sticking and other problems during the drying step. Moreover, using such emulsifiers can also impair the taste and texture of food products, depending on the form used. In addition, since most of such emulsifiers are synthetic products they are sometimes undesirable for use. JP2003-238396A mentions water-soluble macromolecules such as starch, dextrin and gum arabic as emulsifiers, but emulsified compositions using these water-soluble macromolecules instead of synthetic emulsifiers have not been produced, and it is unknown whether a stable coenzyme Q10-containing emulsion can be obtained by this method.
On the other hand, for dispersing and emulsifying coenzyme Q10 without using glycerin fatty acid esters or other synthetic emulsifiers, there is a method of dispersing and emulsifying coenzyme Q10 in an aqueous liquid containing a water-soluble substance such as gum arabic, agar, water-soluble corn fiber, starch, gelatin, xanthan gum, casein, dextrin or the like in the presence of an organic acid (JP 2003-55203A). This method can provide products with high bioavailability and stability, but products with even higher coenzyme Q10 contents are desired.
There is a method for producing emulsified powders by adding processed starch, saccharides and water to fat-soluble substances for emulsification and then drying the mixtures, and emulsified powdered products have been disclosed that contain about 52% tocopherol acetate (JP11-196785A). Still, the compositions obtained when this method is applied to coenzyme Q10 are unsatisfactory from the standpoint of emulsion stability.
Thus, a high demand remains for a coenzyme Q10-containing composition that employs no glycerin fatty acid esters or other synthetic emulsifiers, that can include a high content of coenzyme Q10, and that can provide high stability and bioavailability for coenzyme Q10.